The ability to identify individual tagged items contained within external packaging obscured from visual inspection may improve efficiency and management of stock. Furthermore, the ability to determine an item's environmental conditions within large bulk packaging rapidly and non-invasively can improve stock management, mitigation of product damage and maintenance of sterile environments.
Existing penetrating radiation identification and security tags (including terahertz (THz) and microwave) suffer from serious impediments to usability and thus their ability to address the above issues. These impediments may arise due to the use of partial transmission or dependence on focused beams. For example, retrieving data from a tag by transmitting radiation through the tag requires a large receiver to detect the transmitted radiation. Such a receiver adds cost and complexity to a system and renders the tag unusable if it is positioned in close proximity to a non-transmissive object (e.g. any metal or moisture-containing material within the packaging). For similar reasons, the use of a reflective surface or a perforation contrast for tags may not provide sufficient contrast for reading the tag. This limits the distance from which the tag may be read and precludes it from use on a wide range of products for which it may otherwise be useful, such as appliances and foodstuffs.
Additionally, focused and highly coherent beams or penetrating laser beams, required for reading some existing tags, are expensive to produce, require bulky equipment with extensive cooling systems to operate, and provide only a narrow readable angle. Such reader-tag systems require accurate targeting of the tag, and thus are only usable at close range, as the resolution rapidly degrades over distance. Accordingly, there is a need for a tag that is readable, preferably from a single handheld instrument, via high contrast reflection over a wide detection angle.